Komon-umiushi split into two species (Goniobranchus aureopurpureus + G. cf. variatus)
For anyone diving in Japan this feels obvious, but it has now been formalised: komon-umiushi has been split into a northern and a southern species.
https://www.jstage.jst.go.jp/article/specdiv/29/1/29_SD22-30/_article/-char/en
komon-umiushi
Goniobranchus aureopurpureus (Collingwood, 1881)
Effectively a Japanese endemic (the same way ao-umiushi etc. are), distributed broadly from Hokkaidō to Kyūshū.
Diagnostic: rhinophores and gills are purple.
In juveniles, however, the rhinophores often look reddish, so in practice the gill colour is the more reliable character.
minami-komon-umiushi
Goniobranchus cf. variatus (Risbec, 1928)
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